[vsnet-chat 707] Re: Comparison Sequences

["Steve H. Lucas" <76620.1721@compuserve.com>]

Roger Pickard wrote (at 22:59 [GMT] on 1/25/98):

<<"I don't believe that this forum is the correct place to discuss the
proposals in detail at this stage, and not until Dr Mattei has had the
chance to comment formerly on them.   The correct way forward will probably
to be to submit the proposals to other VS organisations for comment before
a more "open" approach is taken"<<

Roger:

Contrary to your beliefs regarding the discussion of the subject matter, I
DO feel that this topic does need open discussion, with some possible
solution implementation by all parties involved. I, of course, do not want
to downplay the importance of any decision that the AAVSO might arrive at,
but I must mention that the opportunity and vehicle that Dr. Kato and the
VSNET offer to us, via open discussions on any subject matter relating to
variable stars is healthy....

As an observer, and research hobbyist of the "ultimate variable
star"....supernovae! My collegues and I have pondered the subject of
comparison magnitudes for many years, and I must add I have been attempting
standarization of comparison stars for over a decade.

When all the visual data points (all observations) regarding phase-decay
magnitudes of a particular supernova event are graphed, an extreme amount
of scatter is noted. However, in one particular event standarized
comparison sequences where used verses a published mean visual light curve
(Doggett and Branch, AJ.,_,90_,2303, 1985)....the event was SN 1991T, and
here are some statistics when that standardization was employed*:

Mean Visual Light Curve                                 

Days          Decline Magnitude       Decay Mag. Per day
_______________________________________________         
0----------
+11.84          +0.5            0.042
+21.05          +1.0            0.047
+31.57          +1.5            0.047
+43.57          +2.0            0.046
+61.84          +2.5            0.040
+81.57          +3.0            0.038

Visual Observations

Days           Decline Magnitude      Decay Mag. Per Day
________________________________________________
0----------------
+14.4           +0.5            0.034
+22.0           +1.0            0.045
+30.0           +1.5            0.050
+42.0           +2.0            0.047
+63.8           +2.5            0.039
+78.0           +3.0            0.038

(*- Note: Over 40% of the observations were sent in by the M-1 Supernova
Search Group of Spain, the rest by members of SUNSEARCH (SUperNova Search).

In conclusion, I would like to mention that while the work of large well
organized Variable Star organizations are extremely valuable to the
astronomical community, there are small groups of us who value our work as
well, and open communication is how we attempt to better our contributions.

Best Regards,

Steve H. Lucas

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